Submersible pumping systems are often deployed into wells to recover petroleum fluids from subterranean reservoirs. Typically, a submersible pumping system includes a number of components, including an electric motor coupled to one or more high performance pump assemblies. Production tubing is connected to the pump assemblies to deliver the petroleum fluids from the subterranean reservoir to a storage facility on the surface.
The motor is typically an oil-filled, high capacity electric motor that can vary in length from a few feet to nearly one hundred feet, and may be rated up to hundreds of horsepower. Prior art motors often include a fixed stator assembly that surrounds a rotor assembly. The rotor assembly rotates within the stator assembly in response to the sequential application of electric current through different portions of the stator assembly. The motor transfers power to the pump assembly through a common shaft keyed to the rotor. For certain applications, intermediate gearboxes can be used to increase the torque provided by the motor to the pump assembly.
Pump assemblies often employ axially and centrifugally oriented multi-stage turbomachines. Most downhole turbomachines include one or more impeller and diffuser combinations, commonly referred to as “stages.” In many designs, each impeller rotates within adjacent stationary diffusers. During use, the rotating impeller imparts kinetic energy to the fluid. A portion of the kinetic energy is converted to pressure as the fluid passes through the downstream diffuser. The impellers are typically keyed to the shaft and rotate in unison.
Often, it is desirable to deploy the pumping system in an offset, deviated, directional, horizontal or other non-vertical well. In these applications, the length and rigidity of the pumping system must be considered as the system is deployed and retracted through curved or angled portions of the well. As the incidence of non-vertical wellbores increases, there is need for a pumping system that can navigate these non-vertical deployments. It is to this and other deficiencies in the prior art that the present invention is directed.